The present invention, in some embodiments thereof, relates to induced pluripotent stem cells (iPS) derived from human pancreatic beta cells, uses thereof and methods of obtaining same.
Type I diabetes is caused by the autoimmune destruction of the pancreatic islet insulin-producing beta cells. Insulin administration does not prevent the long-term complications of the disease, since the optimal insulin dosage is difficult to adjust. Replacement of the damaged cells with regulated insulin-producing cells is considered the ultimate cure for type 1 diabetes. Pancreas transplantation has been successful but is severely limited by the shortage of donors. With the development of new islet isolation and immunosuppression procedures, significant success has been reported using islets from 2-3 donors per recipient [Shapiro A M, Lakey J R, Ryan E A et al. New Engl J Med 2000; 343:230-238]. U.S. Patent Application No. 20080014182 teaches methods of expanding human pancreatic beta cells and subsequent redifferentiation thereof.
However, there remains an urgent need for developing alternatives to human pancreas donors, namely abundant sources of cultured human pancreatic β cells for transplantation.
One alternative to forced expansion of post-mitotic pancreatic β cells is the induction of differentiation of stem/progenitor cells into insulin-producing cells.
Human embryonic stem (ES) cells, derived from the inner cell mass of blastocyst-stage embryos, are capable of unlimited proliferation in vitro while maintaining their potential to differentiate into cells from the three embryonic germ layers. The directed differentiation of embryonic stem cells has generated cells that only produce low amounts of insulin, compared to β cells, and their potential use in transplantation has met with ethical objections.
Human induced pluripotent stem (iPS) cells have been recently generated from human somatic fibroblasts by expression of defined transcription factors. iPS cells have also been generated from other human cell types, including CD34+ cells from peripheral blood, keratinocytes and neural stem cells.
U.S. Patent Application Nos. 20090047263 and 20110014164 teach generation of human iPS cells from, amongst many other somatic cells, pancreatic cells.
Human iPS cells fulfill all current criteria of true human pluripotent stem cells and may offer an alternative cell source for cell replacement therapy and for in-vitro models of genetic diseases. Although human iPS cells were shown to be similar to human ES cells, as judged by expression of pluripotency genes and their ability to generate embryoid bodies (EBs) and teratomas, mounting evidence suggests that iPS cells differ from ES cells in gene expression profiles, persistence of donor-cell gene expression, differentiation abilities, tumorigenicity, stability of imprinted gene expression, and disease modeling. Recently, it has been shown that following the reprogramming of mouse iPS cells, an epigenetic memory is inherited from the parental cell [Kim, K et al. Nature. 467, 285-290 (2010); Polo J M et al., Nat. Biotechnol. 28(8), 848-855 (2010)].
Some emerging works also show a unique DNA methylation signature that is derived from a parental human cell following reprogramming [Doi A., et al. Nat Genet. 41 1350-1353 (2009); Kim Ey., et al. Cell reprogram. 12 627-639 (2010); Lister et al. Nature 471, 68-73 (2011)].
Stadtfeld et al., [Current Biology 18, 890-894, 2008] teaches generation of iPS cells derived from mouse pancreatic beta cells in order to establish that fully differentiated cells may be used to generate iPS cells.
Other background art includes Eminli, S. et al. Nat. Genet. 41, 968-976 (2009), Kim et al., Nature. 467, 285-290 (2010); and Polo et al., Nat. Biotechnol. 28(8), 848-855 (2010).